This invention relates to a method and apparatus for filling, moving and closing packaging trays, and more particularly to the controlled movement of a filled package prior and subsequent to the sealing of the filled packages for preventing the spilling of contents or the fracture of the packages being filled and sealed.
U.S. Pat. 5,065,563 discloses a packaging machine in which packaging trays are moved by push bars attached to driving chains which form a closed loop. The trays are displaced one behind the other into a filling station and then out of the filling station to discharge the closed packaging trays. The trays are pushed into the filling station and then the pusher is moved backward away from the tray in the filling station to permit vacuum welding meaning to weld thermoplastic film onto the tray in the filling station, and thereafter reversing the movement of the pusher so that the tray is again contacted by a pusher and moved out of the filling station and to move another tray into the filling station. The purpose of the movement is to move the pusher out of the way of the welding apparatus so as not to interfere with the welding after the package has been filled in that station. The problem with this approach is that the combination of the filling and welding station is impractical and the switch controlled movement disclosed would not be appropriate for a package filled in a loading area which is then transported to a welding station in view of the fact that the movement of the pushers could spill liquid contents in the movement or on the other hand damage or fracture the filled package prior or subsequent to sealing.